Occurrences of Polar Pesticide Contamination in Niger River Valley and Its Tributary the Mekrou River, Using POCIS Passive Samplers and Survey of Agricultural Practices (Niger Republic)

Abstract

\n The increase in food needs due to high population growth in Niger has led to the intensification of urban agriculture and increased use of pesticides. The objective of this study is to assess the polar pesticide contamination of the Niger River and its tributary, the Mekrou River, in Niger, using both grab sampling and POCIS (Polar Organic Chemical Integrative Samplers) and evaluate their ecological risks in the waters. Two water sampling campaigns were carried out during the rainy and dry seasons. The samples were analyzed by liquid chromatography coupled with mass spectrometry (HPLC/MS) and allowed the detection of compounds with concentrations above the WHO guide values and the EU directive: diuron with 3281 ng/L (EU quality guideline: 200 ng/L), atrazine with 1476 ng/L (EU quality guideline: 600 ng/L) and acetochlor with 255 ng/L (EU quality guideline: 100 ng/L). Diuron and Atrazine show a high ecological risk for aquatique environment. The main source of this water contamination is the intensive use of pesticides in urban agriculture near the city of Niamey and in an intensive cotton farming in the Benin. The results of surveys showed the influence of poor pesticide application practices and seventy percent (70%) of the pesticides used are not approved by the Interstate Committee for Drought Control in the Sahel (CILSS) and some are prohibited in Niger. These contaminations may raise concerns about the health of farmers along the Niger River and the Mekrou River.